Audacity Projects file format

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mikezz1
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Joined: Wed Dec 23, 2020 1:17 am
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Audacity Projects file format

Post by mikezz1 » Tue Jan 12, 2021 10:35 pm

Is an Audacity project file (Save Project, Save As Project) a lossless format?

I noticed if I "Save Lossless Copy of Project' there is a folder created with a single .wav file named the same as the .aup file.
If I open the project, make a change or add a label and save (cntrl-S), there is a new subfolder titled 'e08' along with the .wav file.
The e08 folder is about twice the size of the .wave file.

I understand when you make an original recording that you might want a single .wav file for safe keeping but i'm trying to determine the best way to save when working on projects without taking up more disk space than I need to.
Thanks

DVDdoug
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Re: Audacity Projects file format

Post by DVDdoug » Tue Jan 12, 2021 11:08 pm

Audacity uses 32-bit floating-point for internal processing (and for projects) so it takes twice the space as a "similar" 16-bit file.

The main advantage of floating point is that it can go over 0dB, whereas regular integer formats are hard-limited to 0dB and they will clip (distort) if you "try" to go over. For all practical purposes, floating point has no upper (or lower) limit. And there are advantages to using floating point with digital signal processing.

The size of uncompressed audio data is easy to calculate if you know that there are 8 bits in a byte - For example, CD audio is 44,100 samples per second, 16-bit, stereo. 1 second "CD quality" "audio is 44.1K x (16/8) x 2 channels = 176.4 kilobytes.

kozikowski
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Re: Audacity Projects file format

Post by kozikowski » Wed Jan 13, 2021 12:23 am

without taking up more disk space than I need to.
There's the voice of doom. Audacity (and many other production editors) use up drive space way faster than you think. If you know you're running out, this is not the machine for editing your show. You may be one of the forum posters who want to know why their show won't open at all, crashes, or opens up damaged and featuring error messages.

Do you have solid state drives or spinning metal? Both (hopefully)? I use SSDs for real time day to day use and massive external spinning metal drives for backups.

Any important work should appear in 2 (two) separate places. Two folders on your internal drive doesn't count.


I think the posted Project instructions are a little behind the parade. The current Lossless Project makes a killer perfect WAV file in addition to the AUP Project Manager file and—I thought—the usual _DATA folder and thousands of tiny (6 second) AU sound files. I think the Wiki instructions may be scrambled on this point. This latest change/addition was an effort to keep the bloodletting down to a minimum if an Audacity Project goes Hindenburg. The WAV file is likely to survive the flames.

This will all go away shortly when the new Audacity comes out, but it's the process we have right now.

In any event, if you simply Export a WAV file of your work, it's not technically perfect. Audacity will add a tiny bit of dither sound to it to help avoid distortion in the 32 bit to 16 bit conversion process. Audacity is not editing your original files. Audacity converts them to the Audacity internal format, and then it has to convert them back to "normal" when you're done.

It doesn't do any of those tricks to the Project WAV.

Koz

waxcylinder
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Re: Audacity Projects file format

Post by waxcylinder » Wed Jan 13, 2021 9:41 am

kozikowski wrote:
Wed Jan 13, 2021 12:23 am
In any event, if you simply Export a WAV file of your work, it's not technically perfect. Audacity will add a tiny bit of dither sound to it to help avoid distortion in the 32 bit to 16 bit conversion process. Audacity is not editing your original files. Audacity converts them to the Audacity internal format, and then it has to convert them back to "normal" when you're done.
That's if you use the default 16-bit export setting for WAV -if instead you opt for WAV export at 32-bit float then no dither will be applied (BUT the resultant WAV file will be twice the size).

As Koz says the key to backups is not to reduce their quality but to use large (often external disks for such backups) - thereby reducing the file space load on your work disk.

I have an HP Envy that has onboard a 256 SSD and a 1TB spinning metal disk. I run active projects on the SSD and do primary backup to the 1TB onboard disk.

I also have secondary backup in the form of two external 2TB disks (footprint so small they fit in a pocket or in my case desk-drawer. Being a very cautions type I also have tertiary backup in a 3rd 2TB disk that lives in a city 1,000 miles away as my off-site backup.

(BTW those 2TB disks are quite cheap these days - I paid around UK£70 for each of them 0 a small price to pay to safeguard all the hard work I have done with Audacity and Photoshop with my photos.)

Peter.
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